1. Field of the Invention
The present invention relates to flux mapping systems for nuclear reactors and, more particularly, to a flexible and highly reliable flux mapping system with a simple architecture.
2. Description of the Related Art
Nuclear reactors include incore and excore detectors, i.e., detectors which are positioned inside the nuclear reactor core and detectors which are outside the core but inside the containment. Flux detectors, for example, may be used both inside the core and outside the core. In both cases, the flux detectors measure neutron flux emanating from the fuel in the core. The incore flux detectors are inserted into thimbles which pass through the core. The incore flux detectors are then drawn out of the core at a predetermined rate to produce a flux map along each thimble.
A pressurized water nuclear reactor typically has approximately sixty thimbles, but may have only four detectors. Multiple-path selectors are used to route the detectors into the thimbles. All or a portion, e.g., a quadrant, of the core may be mapped at a given time. Typically, all, e.g., four detectors are inserted into different thimbles simultaneously so that the map can be produced as quickly as possible while conditions in the core undergo little change.
Prior art flux mapping control systems were completely custom designed computer systems with high reliability to ensure that the flux mapping operation was being performed correctly. However, such systems were sometimes designed with excessively tight parameters, so that at times no flux mapping could be performed, even one with somewhat suspect results. In addition, changes to the parameters often required programming changes which could only be performed by the manufacturer of the flux mapping system and not by the operator. As a result, prior art flux mapping systems often provided lower availability than desired.